Obrázky na stránke
PDF
ePub

and soon after very widely propagated over Europe, by the abilities and eloquence of one of his scholars, the celebrated Peter Abelard. According to these philosophers, there are no existences in nature corresponding to general terms, and the objects of our attention in all our general speculations are not ideas but words.

In consequence of this new doctrine, the schoolmen gradually formed themselves into two sects; one of which attached itself to the opinions of Roscelinus and Abelard, while the other adhered to the principles of Aristotle. Of these sects, the former are known in literary history by the name of the Nominalists, the latter by that of the Realists.

As it is with the doctrine of the Nominalists that my own opinion on this subject coincides, and as I propose to deduce from it some consequences, which appear to me important, I shall endeavour to state it as clearly and precisely as I am able, pursuing, however, rather the train of my own thoughts, than guided by the reasonings of any particular author.

I formerly explained in what manner the words, which in the infancy of language were proper names, became gradually appellatives, in consequence of which extension of their signification, they would express, when applied to individuals, those qualities only which are common to the whole genus. Now it is evident, that with respect to individuals of the same genus, there are two classes of truths; the one, particular truths relating to each individual apart, and deduced from a consideration of its peculiar and distinguishing properties-the other, general truths deduced from a consideration of their common qualities, and equally applicable to all of them. Such truths may be conveniently expressed by means of general terms, so as to form propositions, comprehending under them as many particular truths as there are individuals comprehended under the general terms. It is farther evident, that there are two ways in which such general truths may be obtained; either by fixing the attention on one individual, in such a manner that our reasoning may involve no circumstances but those which are common to the whole genus, or, (laying aside entirely the consideration of

things,) by means of the general terms with which language supplies us. In either of these cases, our investigations must necessarily lead us to general conclusions. In the first case, our attention being limited to those circumstances in which the subject of our reasoning resembles all other individuals of the same genus, whatever we demonstrate with respect to this subject must be true of every other to which the same attributes belong. In the second case, the subject of our reasoning being expressed by a generic word, which applies in common to a number of individuals, the conclusion we form must be as extensive in its application, as the name of the subject is in its meaning. The former process is analogous to the practice of geometers, who, in their most general reasonings, direct the attention to a particular diagram; the latter to that of algebraists, who carry on their investigations by means of symbols.1 In cases of this last sort, it may frequently happen from the association of ideas, that a general word may recall some one individual to which it is applicable, but this is so far from being necessary to the accuracy of our reasoning, that excepting in some cases, in which it may be useful to check us in the abuse of general terms, it always has a tendency more or less to mislead us from the truth. As the decision of a judge must necessarily be impartial, when he is only acquainted with the relations in which the parties stand to each other, and when their names are supplied by letters of the alphabet, or by the fictitious names of Titius, Caius, and Sempronius; so, in every process of reasoning, the conclusion we form is most likely to be logically just, when the attention is confined solely to signs, and when the imagination does not present to it those

These two methods of obtaining general truths proceed on the same prin ciples, and are, in fact, much less different from each other than they appear to be at first view. When we carry on a process of general reasoning, by fixing our attention on a particular individual of a genus, this individual is to be considered merely as a sign or representative, and differs from any other sign

only in this, that it bears a certain resemblance to the things it denotes.The straight lines which are employed in the fifth book of Euclid to represent magnitudes in general, differ from the algebraical expressions of these magnitudes, in the same respects in which picture writing differs from arbitrary characters.

individual objects which may warp the judgment by casual associations.

To these remarks, it may not be improper to add, that although, in our speculations concerning individuals, it is possible to carry on processes of reasoning, by fixing our attention on the objects themselves, without the use of language; yet it is also in our power to accomplish the same end, by substituting for these objects words or other arbitrary signs. The difference between the employment of language in such cases, and in our speculations concerning classes or genera, is,—that in the former case the use of words is, in a great measure, optional; whereas, in the latter, it is essentially necessary. This observation deserves our attention the more, that, if I am not mistaken, it has contributed to mislead some of the Realists, by giving rise to an idea that the use of language, in thinking about universals, however convenient, is not more necessary than in thinking about individuals.

According to this view of the process of the mind, in carrying on general speculations, that IDEA which the ancient philosophers considered as the essence of an individual, is nothing more than the particular quality or qualities in which it resembles other individuals of the same class, and in consequence of which, a generic name is applied to it. It is the possession of this quality that entitles the individual to the generic appellation, and which, therefore, may be said to be essential to its classification with that particular genus; but as all classifications are to a certain degree abitrary, it does not necessarily follow that it is more essential to its existence as an individual, than various other qualities which we are accustomed to regard as accidental. In other words, (if I may borrow the language of modern philosophy,) this quality forms its nominal, but not its real essence.

These observations will, I trust, be sufficient for the satisfaction of such of my readers as are at all conversant with philosophical inquiries. For the sake of others, to whom this disquisition may be new, I have added the following illustrations.

I shall have occasion to examine, in another part of my work, how far it is true, (as is commonly believed,) that every process of reasoning may be resolved into a series of syllogisms; and to point out some limitations with which, I apprehend, it is necessary that this opinion should be received. As it would lead me, however, too far from my present subject to anticipate any part of the doctrine which I am then to propose, I shall, in the following remarks, proceed on the supposition that the syllogistic theory is well-founded; a supposition which, although not strictly agreeable to truth, is yet sufficiently accurate for the use which I am now to make of it. Take, then, any step of one of Euclid's demonstrations; for example, the first step of his first proposition, and state it in the form of a syllogism.— "All straight lines, drawn from the centre of a circle to the circumference, are equal to one another." "But A B and CD are straight lines, drawn from the centre of a circle to the circumference. Therefore, A B is equal to CD."-It is perfectly manifest that, in order to feel the force of this conclusion, it is by no means necessary that I should annex any particular notions to the letters A B or CD, or that I should comprehend what is meant by equality, or by a circle, its centre, and its circumference. Every person must be satisfied that the truth of the conclusion is necessarily implied in that of the two pre-mises, whatever the particular things may be to which these premises may relate. In the following syllogism, too :-" All men must die ;-Peter is a man;-therefore Peter must die;" the evidence of the conclusion does not in the least depend on the particular notions I annex to the words man and Peter; but would be equally complete if we were to substitute, instead of them, two letters of the alphabet, or any other insignificant characters. "All X's must die;-Z is an X;-therefore Z must die;"-is a syllogism which forces the assent no less than the former. It is farther obvious, that this syllogism would be equally conclusive if, instead of the word die, I were to substitute any other verb that the language contains; and that, in order to perceive the justness of the inference, it is not even necessary that I should understand its meaning.

In general, it might be easily shewn that all the rules of logic, with respect to syllogisms, might be demonstrated without having recourse to anything but letters of the alphabet; in the same manner (and I may add, on the very same principles) on which the algebraist demonstrates, by means of these letters, the various rules for transposing the terms of an equation.

From what has been said, it follows that the assent we give to the conclusion of a syllogism does not result from any examination of the notions expressed by the different propositions of which it is composed, but is an immediate consequence of the relations in which the words stand to each other. The truth is, that in every syllogism the inference is only a particular instance of the general axiom, that whatever is true universally of any sign, must also be true of every individual which that sign can be employed to express. Admitting, therefore, that every process of reasoning may be resolved into a series of syllogisms, it follows that this operation of the mind furnishes no proof of the existence of anything corresponding to general terms, distinct from the individuals to which these terms are applicable.

These remarks, I am very sensible, do by no means exhaust the subject, for there are various modes of reasoning to which the syllogistic theory does not apply. But in all of them, without exception, it will be found, on examination, that the evidence of our conclusions appears immediately from the consideration of the words in which the premises are expressed, without any reference to the things which they denote. The imperfect account which is given of deductive evidence, in the received systems of logic, makes it impossible for me, in this place, to prosecute the subject any farther.

After all that I have said on the use of language as an instrument of reasoning, I can easily foresee a variety of objections which may occur to the doctrine I have been endeavouring to establish. But, without entering into a particular examination of these objections, I believe I may venture to affirm, that most, if not all, of them take their rise from confounding reasoning or deduction, properly so called, with certain

VOL. II.

M

« PredošláPokračovať »